I have a Samsonite spinner carry-on that I love which I got about two years ago as a gift. While not new to air travel, I was on a plane about once a year, if that. Since getting the luggage I've flown a bit more (but still not a lot, maybe only four or five trips). I came to realize that while the luggage was advertized as a carry-on size, it was too big. I measured it and with its wheels it's about 23 inches. On long hauls with bigger planes it usually does fit in the overhead bins, but almost always I have to check it on smaller planes. I usually fly Delta or United, tho sometimes US Airways or American (I live in the US). (Travel is both national and international.)

So my question is, do others on this forum travel with over-sized carry-on luggage with usually no problem? Or is it a problem? I don't often have things in the carry-on that can get damaged or broken very easily, I put those things in my personal item, so if it does have to get checked I don't worry a lot. I'm just curious what other people's opinions or experiences were.

I don't have much money to replace the carry-on, thus my question. I'm trying to decide if I should continue using it or save my pennies to buy a new one as soon as possible that is a smaller size (but don't want to really give this carry-on up.)

Wheels are the devil in the details! You know this now.
To make a carry-on fit pretty much across the board you are looking at getting a 20" carry-on so the 1.50" or so of wheels bring you up to the max 22"
Some international carriers will stick you on weight for the carry-on so the additional weight from the wheels and hardware can cut your carry-on weight in almost half.

My carry on is a backpack that holds 3~ days of clothes and my laptop and most other 'need it now' items. Fights in all over heads(dash8 to A380) and MOST underseat storage areas.

Most of the time I travel with two items, a carry-on and a personal item. They are both max for what is allowed but not over. I would not travel with something that is over the allowances as I do not want to have to check items (no fee for me but I want to walk off the plane and roll). If you do, you can get away with it but no guarantees. You should be prepared for the airline to tell you they have to check it.

Your question is somewhat difficult to answer with 100% certainty because of the unpredictability of US domestic airlines requiring that passengers place their baggage in a sizer. I've never had to do it, and a lot of sizers in US airports appear to be gathering dust, but there are occasional reports here at FT that an airline does it at a specific airport for a day or two and then stops. So long as GAs eyeball your bag (if they even pay attention), you're not so far over the limit that you're likely to have to check your bag other than when the overheads are so full that you'd have to gate check anyway.

Another complicating factor: a similar inconsistency with international carriers that appears based on how much in fees they want to generate from baggage. The big carriers, like BA, seem to have a similar approach to US domestic airlines since I've never really seen them consistently force passengers to use sizers. Airlines like RyanAir, on the other hand, make up a lot of money lost from their low-fare tickets on baggage so they're measuring and weighing in an intense effort to increase the airline's profit. Throw in some other airlines where there are even more stringent restrictions on size and weight to begin with, and you may find that a bag that would definitely meet size and weight requirements here may not there.

Given that funds are a little tight right now, I wouldn't run right out and buy another bag just to trim a couple of inches. I would think about maximizing any "personal item" you might carry--even a rapacious carrier like Spirit still allows a free personal item. I try to pack mine so that I have one change of clothes and my toiletries in case what I thought was going to be a carryon becomes a checked bag that then becomes a lost, checked bag (don't laugh, Southwest once lost a checked bag on a nonstop flight from MCO to ORF where I was in the terminal two-and-a-half hours early).

I might also keep in mind that airlines are probably going to increase their vigilance about these issues and be on the lookout for appropriate bags when you do eventually decide to replace your current bag.

No--and neither should you. Don't ruin it for the rest of us and give them an excuse to crack down on us all.

Don't be quite so sure. Many manufacturers advertise their bags as fitting within airline carryon requirements, not mentioning that they've picked the IATA standard of 50 linear inches that many airlines don't follow. Most US domestic airlines run around 45 linear inches as a max. The advertising isn't incorrect; it just isn't very helpful. I suspect our OP got caught by this kind of advertising.

In addition, I've learned that soft-sided luggage may expand as much as 10% when fully packed over its advertised size. So that bag that says it's 45 linear inches may actually be almost 50 if stuffed to the gills.

The inconsistency of luggage advertising as well as domestic enforcement of size and weight requirements makes it difficult to purchase a bag that fits all airline requirements. I take a tape measure with me now whenever I need to purchase a bag in the store, and if I'm ordering a soft-sided bag online, I keep in mind my 10% rule, both when buying and when packing.